This study is being conducted to study the effect of nabilone (a synthetic cannabinoid)on spasticity in spinal cord injured persons.The study will be a phase 2, randomized, placebo-controlled crossover study. Each eligible subject will participate for 26 weeks.Subjects will be randomized to receive either nabilone or placebo during phase 1 of the study. Study drug will be titrated up from 0.5mg daily to a maximum of 3.0 mg daily over the first 11-week phase. Following a 4-week washout period, subjects will be crossed-over to the opposite arm for another 11 week treatment period (phase 2).